Tannase (tannin acyl hydrolase, EC3.1.1.20) is an enzyme that hydrolyzes a depside bond of tannins. In the food industry, tannase is used for prevention of cream down in tea beverages, prevention of lee in fruit juice beverages, clarification of beer, and the like.
Production of tannase by bacteria, yeasts, and filamentous fungi has been reported in large numbers so far (Non-patent Document 1). There are many reports about the genus Aspergillus and the genus Penicillium for the filamentous fungi. Chemoenzymatic properties, an amino acid sequence and a gene encoding tannase have been revealed for tannase derived from Aspergillus oryzae (see Patent Documents 1 and 2, and Non-patent Document 2).
The tannase described in Patent Document 1 has mild acidity such as an optimum pH range around from 5.0 to 5.5, and an optimum temperature range of around 40° C., and is deactivated within 10 minutes at a high temperature such as higher than 60° C. Therefore, the tannase is reacted under very limited conditions in industrial applications. The tannase described in Patent Document 2 is excellent in thermostability, a residual activity after treatment at 65° C. for 10 minutes in a citric acid buffer solution (pH 5.5) is 80% or more, and an optimum temperature range is from 60 to 80° C., and thus, the defect of the tannase described in Patent Document 1 is overcome, but production of a recombinant was only reported and production of a non-recombinant is not confirmed. Therefore, for applications in the food industry, safety confirmation according to “safety evaluation standard of additives produced in use of genetically modified organisms” is required (Non-patent Document 3). In addition, there is deep-seated rejection against genetically modified foods in Japan. Accordingly, the tannase cannot be recognized as one that is immediately applicable in the food industry.
On the other hand, tannase excellent in thermostability, which has an optimum temperature of 60° C. or higher, (see Non-patent Documents 4 and 5) was also reported. However, existence of such tannase has been merely confirmed and the amino acid sequence thereof, a gene encoding the tannase, chemoenzymatic properties thereof, and the like have not been revealed and a practical application has not been achieved yet.